1. Technical Field to Which the Invention Pertains
The present invention relates to an efficient process for producing an optically active compound having high optical purity by using, as a catalyst in an asymmetric Michael reaction, a transition metal complex having an optically active nitrogen-containing compound as an asymmetric ligand.
2. Prior Art
Optically active compounds obtained by an asymmetric Michael reaction are useful as synthetic intermediates for pharmaceuticals, etc. For example, an optically active ketone obtained by an asymmetric Michael reaction of an enone can be used as a synthetic intermediate for a prostaglandin, etc. With regard to a process for synthesizing these optically active ketones, various processes have been developed, and known examples of asymmetric Michael reactions using an asymmetric catalyst are as follows. For example, there are asymmetric lanthanoid complex catalysts (ref. JP, A, 7-265709, JP, A, 8-291178, JP, A, 11-240865, JP, A, 2001-31682, or JP, A, 2002-69076), and asymmetric aluminum complex catalysts (ref. JP, A, 2001-31682 or JP, A, 8-319258). Furthermore, asymmetric rhodium complexes (ref. JP, A, 10-130286) and asymmetric hafnium, titanium, zirconium complex catalysts (ref. JP, A, 2001-252567) have been reported.
The asymmetric lanthanoid catalysts, which have a lanthanoid as a center metal, have a different metal such as lithium in the catalyst molecule, and it is thought that the lanthanoid and lithium activate a Michael donor and a Michael acceptor respectively. It is therefore necessary to have two different types of metal in the molecule, and it is thus necessary to design an asymmetric metal complex having a complicated structure.
These processes cannot therefore be always said to be highly practical since it might be difficult to prepare the catalyst, the catalyst might have a stability problem, it might be necessary to use a large amount of catalyst, or it might be necessary to carry out the reaction at low temperature or for a long time.
The present invention has been achieved under the above-mentioned circumstances, and it is an object thereof to provide an efficient process for producing a Michael addition product having high optical purity by an asymmetric Michael reaction using a catalytic amount of an asymmetric source under mild conditions.